Therapies with human embryonic
stem cells
Several diseases such as Parkinson and
Juvenile Diabetes Mellitus are resulting from
the death of dysfunction of one or some cell
types. So, the replacement of these cells for
tissues produced from human embryonic stem
cells could provide a long lasting therapy.
The capacity for human embryonic stem
cells to differentiate into several cell types
in vitro allows that these cells may become an almost unlimited source for the
production of tissues that could be used
for transplant and for several diseases.
However, therapies with embryonic stem
cells have not been performed yet. These
cells must be cultivated and differentiated in
vitro for long periods before being transplanted, since once injected in its undifferentiated form they can multiply and differentiate
in an uncontrolled way, giving rise to tumors
instead of the desired therapeutic tissue.

Research on human embryonic stem
cell in Brazil
In Brazil, it has been recently approved the
law for the researches with human embryonic
stem cells, but many ethical issues regarding
the topic are discussed. As these cells until
now are obtained from the inner mass cell
of the blastocyst, i.e. from an embryo, it is
necessary the destruction of these embryos
to obtain these cells. Some conflicts between religion and science are inevitable. Most
of the researches are performed with lines
of human embryonic stem cells, i.e. these
cells had already been obtained and expanded in vitro for trading. In Brazil there are
only two centers of authorized researches
to establish embryonic stem cells lines that
can be used by other centers, which becomes a controlled and regulated proceeding.

This material was produced as part of the subject of a
post-graduate program at the Medical School of Ribeirão
Preto (FMRP)

Did you know that some researchers
have differentiated human embryonic stem cell into blood cells?
At the Regional Blood Center of RibeirĂŁo
Preto researches on human embryonic stem
cells are performed. Following specific methodologies, these cells can be differentiated
into red blood cells, granulocytes, megakaryocytes, natural killer cells and lymphocytes.
The cell produced by some research groups
are very similar to blood cells found in the
adult organism, but they still present features very similar to embryonic and fetal phases. These discoveries constitute models for
the study of the genetic mechanisms involved in the production of blood cells and in
the origin of blood disorders. It is necessary
to consider that the conditions used in the in
vitro production of these cells are not identical to the in vivo organism. Thus, the issue is
whether these cells perform the same work
of the cells found naturally in the human organism. Currently, many studies have been
conducted to answer this issue.
The production of blood cells for clinical
use depends on the solution of some problems such as: risk of tumor when injected
in vivo, chromosomal instability of these
cells during their cultivation, presence of
contamination derived from products of animal origin used in the institute, cultivation
and differentiation of embryonic stem cells,
large scale production and low cost, and incompatibility between the cells generated
and those from the donor.

What are stem cells and what are
the types?
Stem cells are cell without specific function,
with high potential of multiplying, which differentiate and specialize giving origin to mature and functional cells of the adult tissue.

The stem cells are divided into: embryonic and somatic. Embryonic: as the name
says, cells found in the embryonic period.
They are pluripotent, since they are able to
multiply unlimited and differentiate into all
the cells that compose the adult individual,
but are unable to form the placenta and the
fetal annex. Somatic: are found in the tissues of an adult individual and are able to
differentiate into only some types of specific
cells.

How do they raise and where
are human embryonic stem cells
found?
Do
you
remember
embryonic
development?
After the fertilization of the egg by the
sperm, there is the formation of a cell with
46 chromosomes, named zygote, the beginning of the embryonic development.
The mitotic division of the zygote into two
daughter cells called blastomeres begins
a few days after fertilization (see the scheme beside â&#x20AC;&#x201C; figure 1). At the initial stages
of this process, the multiple cell divisions
of the blastomeres take to a stage known
as morula, which consists of a massive
Figure 1: Scheme of embryonic stem cells origin
structure of cells. Following, there is the formation of blastocysts or blastula that has the
inner cell mass and an external cell mass.
The cells of the inner part form the fetus and
some extra-embryonic tissues such as amnion
and allantois. Besides, they have an unlimited
potential of proliferation and can differentiate
into all the cell types that compose that adult
organism, they are, pluripotent stem cells
or embryonic. The cells that constitute the
external layer of the blastocyst will give rise to
tissues related to the placenta.
In 1998, for the first time, James Thomson
and colleagues took cells from the inner cell
mass of human blastocysts and cultivated
them in vitro, giving rise to the first line of
embryonic stem cells.
Figure 2: Colonies of embryonic stem cells
cultivated in vitro

Folhetins-Human Embryonic Stem Cells

Did you know that some researchers have differentiated human embryonic stem cell into blood cells? At the Regional Blood Center of Ribeirão Preto researches on human embryonic stem cells are performed. Following specific methodologies, these cells can be differentiated into red blood cells, granulocytes, megakaryocytes, natural killer cells and lymphocytes.